Control systems for controlling a wind turbine

ABSTRACT

A distributed module control system for controlling a wind turbine using multiple controls and monitors comprising multiple modules that include microcontrollers, and having data input terminals and data output terminals; high level logic circuitry interconnecting the modules via selected data input and data output terminals; and certain modules also connected with the turbine monitors and controls to control operation of the wind turbines in response to monitoring of turbine operation.

BACKGROUND OF THE INVENTION

This invention relates generally to control systems that employdistributed data (intelligence) processing, and more particularly towind turbine control systems wherein multiple microprocessors areemployed instead of a central processor.

Historically, microprocessor based wind turbine control systems havebeen designed, developed and manufactured using a single centralprocessing unit which handles all input, output, calculation, logic, anddata manipulation functions. Such centralized processing requiresmultiplexed input/output functions and relatively large interrupt drivenprograms to handle the complexity of wind turbine control. This designapproach has certain objectionable aspects due to the following reasons:

1. The processors' inability to monitor and control each input/outputport simultaneously. Although some real time data can be processed, thelarge input/output requirements mean that most functions will beallocated on a shared priority basis.

2. Because of the turbine controller's large requirements forinput/output data, peripheral integrated circuits are required to expandthe functional ability of the processor. These peripheral circuitsincrease the complexity of the central processing unit design,decreasing its long term reliability and increasing its maintenancecost.

3. Such complex centralized designs also require relatively largeprograms, which are much more difficult and time consuming to analyze,test and debug. Software development time can easily outstrip hardwaredevelopment time in such large programs, and therefore projectmanagement can be complicated due to problems associated with judgingthe time required for such programming.

4. Traditionally, the manufacturing method for such centralized designhas been to locate all of the electronic components on a single printedcircuit board making maintenance cumbersome, time consuming, andrelatively expensive.

A typical centralized processor employs an address and data bus toexpand the functional ability of the processor through such externalintegrated circuits, such as a Peripheral Interface Adapter (PIA),External Random Access Memory, special timing circuits, serial portadapters, and Analog to Digital Conversion. In addition, most processorbased control systems used in wind turbine controller environmentsrequire external Read Only Memory for the program residence. In atypical wind turbine application, the program residence can occupy asmany as three or four ROM chips. External Random Access Memory for datastorage and manipulation can also occupy several chips, and it is notuncommon to see two or three PIA chips in order for the processor todeal with the large input/output requirements of the control system.Other external peripheral integrated circuits can include special timerchips, and serial port adapters. As the number of these chips grows, sodoes the control bus logic, thereby increasing the complexity of thedesign.

SUMMARY OF THE INVENTION

It is a major object of the invention to provide a distributedintelligence control system, particularly suitable for wind turbinecontrol, that overcomes the above described problems and disadvantages.

As will appear, the invention basically includes:

a) multiple modules that each include a microcontroller, and having datainput terminals and data output terminals,

b) high level logic circuitry interconnecting the modules via selecteddata input and data output terminals, and

c) certain modules also connected with the turbine monitors and controlsto control operation of the wind turbine in response to monitoring ofturbine operation.

The microcontrollers employed differ from a microprocessor primarilybecause the functions required for operation as an instrument orcontroller are integrated onto one chip. This does not mean thatmicrocontrollers normally outperform microprocessors; on the contrary,most microcontrollers have a simpler instruction set and are moredifficult to expand since their address and data bus is normally notreadily available at the output pins. However, since the present controlsystem is divided up into only a few small individual blocks, themicrocontrollers can easily handle their duties without the use of otherperipheral integrated circuits, with the possible exception of an analogto digital converter.

In the inter-module and input/output communication system employed,communication between modules, external sensors, switches and indicatorsis accomplished with the use of high voltage, (high level) logicsignals. Such high level logic helps achieve good noise immunity,especially since many of these signals must travel up the turbine towerin parallel with motor and generator power cables.

Each microcontroller is operated asynchronously, in that each has itsown internal clock and is not synchronized with the previous device.Such a system can be accomplished with good definitions of theindividual blocks provided. Each is completed with only input and outputlines necessary for operation. This is advantageously achieved within awind turbine control system because of the unique and individual dutiesnecessary, such as generator mains control, propeller overspeedmonitoring and control, AC mains voltage and frequency monitoring, yawsystem control, wind speed monitoring and control signaling, cable twistmonitoring and control signaling, and other individual functions.

Advantages of the present de-centralized distributed intelligenceapproach include:

1. The system can be easily modularized for easy maintenance, bypackaging the microcontrollers in small individual modules that can beplugged in and out of a mother board. Also modularized are the display,control and fault display modules so that maintenance can be achieved bysimple module replacement Since each module is small and inexpensive,maintenance is greatly simplified. Finally, the expense of replacing anentire centralized control system circuit board, in the event ofmalfunction, is avoided by replacing a much simpler single module.

2. Since individual control functions have associated microcontrollers,and these functions can be and are monitored on a more continuous basisthan in a centralized processor design. Instead of one processorscanning each function, multiple processors scan the same number ofinputs and outputs, thereby increasing the speed of algorithmcompletion.

3. Software requirements are greatly simplified. Each module contains anassembled machine code program as small as 1000 bytes, and typically nolarger than 2000 bytes. The total program space required for all of themodules is smaller than with a centralized approach, which requiresprograms exceeding 16 to 32 kilobytes in size. This reduction greatlyreduces the time required for programming and especially debugging ofthe completed program.

4. Since each microcontroller is a complete system in itself, hardwarecost is reduced by the reduction in the number of peripheral integratedcircuits required. The control system achieves a 40% reduction in actualintegrated circuits over a centralized processor system.

Besides these advantages, the following design objectives are achieved,greatly enhancing system reliability:

1. Control of wind turbine performance in relative extreme environmentalconditions, such as ambient temperatures between -25 to +85 degrees C.,including 100% humidity and a condensing atmosphere. Extendedtemperature range components and a military grade conformal coating forthe circuit boards can be employed. This allows operation of thecontroller in cold, hot and moist environments, without the expense ofan outboard controller heater and its associated control system.Start-up of the controller can be obtained during extremely cold, hot ormoist conditions.

2. By employing only MOS, HCMOS and high voltage bipolar integratedcircuits, a higher level of noise immunity can be achieved, as comparedwith conventional LSTTL and TTL integrated circuits.

3. Grounding and shielding, to achieve lower noise operation, includessingle point grounding for each module, the mother board and finally thentire controller system. Telescoping shields and optical insulatedcontrol lines are also used to help reduce noise and increase commonmode noise rejection. Also employed are bypassing of each integratedcircuit as well as over-voltage protection zener diodes and metal oxidevaristors. These components help to interface microcontrollers directlywith control signals, without need for or use of buffers.

A distributed power supply system is employed by using a standard 28volt regulated supply for main system bus power and distributing it toeach module, which in turn employ their own 5, 12, and 15 voltregulators, internally.

4. Inductive snubbers and other transient overvoltage protection areemployed where solenoid, lamp, and coils are controlled and operated.

5. Logic control of important functions, such as generator mainsconnection and overspeed control, to avoid disconnect of the generatorfrom the mains upon a fault, and a consequent overspeed condition of therotor during high wind speeds.

These and other objects and advantages of the invention, as well as thedetails of an illustrative embodiment, will be more fully understoodfrom the following specification and drawings, in which:

DRAWING DESCRIPTION

FIGS. 1A nd 1B illustrate a control circuit diagram;

FIGS. 2a and 2b also show a control circuit diagram;

FIG. 3 is a circuit diagram showing module-to-module signalling;

FIG. 4 is a block diagram; and

FIG. 5 is a module mounting means.

DETAILED DESCRIPTION

In FIG. 1a, a wind turbine 10 is mounted on a tower 11. It may forexample include three blades 12, defining a 19 meter diameter blade tiprotary trajectory, about a horizontal axis 13. These are examples only.The propeller shaft (low speed) 14 is connected with gearing in a gearbox 15, which is in turn connected via a shaft 16 to an electricalgenerator represented at 17. These elements may be suitably carried at18 and 19 on a platform 20 on the tower. Nacelle 21 encloses theseelements, as shown. Platform 20 is rotatable about a vertical axis 22,as by a yaw motor 23.

As seen in FIG. 2a, the generator output at 17a is electricallyconnected with a three-phase 480 volt utility connection, at 24, asthrough generator contactor and generator overload connections 25 and26.

Eight distributed intelligence control modules are shown in FIGS. 1a,1b, 2a, and 2b. They may be supplied on corresponding self-containedcircuit boards, and are identified and described as follows:

30 Wind Trigger Module (WTM) which provides wind speed control signalsfor the automatic yawing system, automatic cable untwisting system, andhigh wind speed turbine control shutdown from a tower mounted anemometer40, connected at 40a to 30.

31 Auto Yaw Module (AYM) which provides or controls yawing function, vialeads 50 and 51 to the module 32, in response to error signals providedby the output on leads 43 from the nacelle mounted wind vane sensor 44.This negative feedback-type control maintains the propeller axis alignedwith the wind direction. An auto yaw enable signal is applied at 45 fromthe WTM,

32 Auto Untwist Module (AUM), which provides or controls cableuntwisting, functions through a yaw motor mounted sensor. See inputleads 47 from the twist counter 48 that senses twist or rotation of theplatform 20 and nacelle about axis 22. An auto twist disable signal isapplied at 49 to 32 from the WTM. Also, yaw (nacelle) right and leftsignals are applied from the AYM, via leads 50 and 51; and outputs at 52and 53 control a reversing motor starter 54 connected at 55 with the yawmotor 23. Cable twisted fault output at 56 is connected with a faultmodule 33 (see below).

33 Fault Module (FM) provides non-volatile latching fault memory anddisplay status indications, i.e., control of the wind turbine brakesystem. See FM output lead (or leads) 59 connected with a shaft brake(solenoid and actuator) 60 at the turbine. The other inputs to the FMinclude high wind fault input lead 61 from the WTM and yaw motoroverload input lead 62 from yaw motor overload sensor 63. (Switch 63a at63 opens in the event of yaw motor overload, signaling the FM.)

Further, as seen in FIG. 2b, additional inputs to the FM will bereferred to in connection with additional distributed intelligencecontrol modules to be described. The FM output brakes the shaft 14, inresponse to any fault input to the FM.

34 (See FIG. 2a) Generator control unit (GCU) provides control of theoutput of generator 17, as through the generator contactor (see lead29), and the power factor controlling capacitor contactor unit 63 (seelead 64). Unit 63 operates in the same manner as the mains generatorcontactor, except during the condition of a failure in the AC mainsconnection, such as under or over voltage, under or over frequency, orloss of phase, in which case this contactor will be disabled. Duringthese fault conditions, the generator control unit is signaled by theACO line 101 which is the "ORed" output, from 100, (see FIG. 2b) of boththe ACF (AC mains fault) and LOP (Loss of Phase fault) signal lines 88and 92.

The generator control unit also monitors, as via input lead 66, the windturbine brake solenoid control line (BSC) to determine proper status ofits signaling, to prevent the generator from operating as a motoragainst the brake, and to signal an operator in case of a tachometersensor failure.

The last function of the generator control unit is to provide agenerator overspeed output fault signal on lead 67 to the fault module.

Generator overspeed is signaled from a tachometer sensor 70, on lead 71,to the generator control unit.

35 The generator temperature module (GTM) monitors, via sensor 74 andlead 75, the temperature of the generator, and when it has exceeded apreset temperature for a fixed period of time, will in turn signal thefault module of an over-temperature condition. See lead 76.

36 The propeller control unit (PCU) responds to low speed shaft 14 RPM,as via sensor 29 and lead 80, and to signals on brake speed control(BSC) line 66 (see lead 66a): and provides two control outputs, atterminals Propeller Overspeed #1 (POS1) and Propeller Overspeed #2(POS2). See lead 82 from POS1 to the fault module, and lead 59a to lead59 to the turbine brake.

Propeller Overspeed #1 occurs at a lower RPM value then #2. If anoverspeed condition should occur, propeller overspeed #1 will signal thebrake 60 through the fault module to actuate and bring the turbine to astop. By monitoring both RPM and the BSC line, this module will provideoutput Propeller Overspeed #2, if the turbine fails to come to a stop,or continues to accelerate. Propeller Overspeed #2 signals the brake vialine 59a to release allowing the turbine to continue to accelerate to apoint where the propeller overspeed tip-flaps 200 will deploy. Thesefail-safe devices will prevent the destruction of the turbine. Theactivation of Propeller Overspeed #2 will also prevent the brake systemfrom failing.

37 The AC mains module (line voltage and frequency monitor) monitors theutility grid, as via the potential transformer 86 and lead 87. Itprovides an AC mains fault output (ACF) on lead 88 to the fault monitor,when the utility grid frequency exceeds utility standards for frequencyand voltage for utility standards of time.

38 The loss of phase (LOP) monitor senses at 90 and 91 the three-phasecurrents being produced or consumed by the turbine and control system,and signals a loss of a single phase. Monitoring of current is requireddue to the fact that induction generators will produce voltage on abroken leg due to self excitation caused by the power factor capacitors.

It is also noted that the fault module FM receives an input on lead 94from the generator overload connection 26. All of the inputs to the FMare processed, so as to produce a turbine braking signal or signals onlead 59, actuating the brake in case of a sensed fault, as described.Note also a feedback loop at 100 and 101 to the GCU.

FIG. 3 illustrates module-to-module signaling technique, as employed inthe inter-module connection described Note the use of 28 volt high-levellogic signaling at 110, as between MCO (microcontroller) 111 andtransistor 112 to the input at 113 to MCO 113. Transient protection and5 volt logic are provided by the diodes, resistors, and capacitor, asseen at 114-118 shown, whereby the microcontrollers operate at lowvoltage levels, as for example 5 volts.

FIG. 4 illustrates multiple wind turbines 10 and their monitoring andcontrol systems. See multiple modules 30, 31-38 associated with eachturbine, and feedback controls, indicated at 300, from the modules. Suchmodules and controls may be considered to include fault monitors, as at33, as well as additional circuitry, as referred to.

The circuitry, as described, for each turbine may be carried at orproximate the tower for each turbine; and the modules 30-38 are separateand discrete, and have individually replaceable circuit boards. See FIG.5, with side-by-side boards 30a-38a mounted in a chassis 350.

SUMMARY

Traditional wind turbine control systems have been based on acentralized processing system where one microprocessor is called upon tomonitor, signal and control the entire input/output system of theturbine. This type of control system suffers from intensivehardware/software requirements, and large and complex multiplexedinput/output monitoring. By decentralizing the processor power anddistributing this intelligence into several small, defined modulesemploying several individual microcontrollers, as at 30-38, a higherperformance system that is less software intensive, requires less parts,is more reliable, and is much easier to troubleshoot is achieved.

I claim:
 1. In a distributed module control system for controlling awind turbine using multiple controllers and monitors, including turbinemonitors, the combination comprisinga) multiple modules that includemicrocontrollers, and having data input terminals and data outputterminals, b) high level logic circuitry interconnecting the modules viaselected data input and data output terminals, and c) certain modulesalso connected with said turbine monitors and controllers to controloperation of the wind turbine in response to monitoring of turbineoperation.
 2. The system of claim 1 wherein said turbine monitors andcontrollers include:a turbine driven generator control a propelleroverspeed monitor and control an AC mains voltage and frequency monitora turbine yaw system control a wind speed monitor and control a cabletwist monitor and control.
 3. The system of claim 1 wherein the systemincludes multiple wind turbines, and multiple of said elements a), b)and c).
 4. The system of claim 1 wherein said circuitry interconnectingsaid modules includes circuit components connecting between low internalvoltage logic in each microcontroller and high signalling voltage logicpaths between microcontrollers.
 5. The system of claim 1 wherein saidmodules include:i) a wind speed module connected to acquire output datafrom a wind turbine tower mounted anemometer and to provide wind speeddigital data, ii) an auto yaw module connected to acquire output datafrom a turbine nacelle mounted wind vane sensing nacelle directionrelative to prevailing wind direction, and to provide error data, iii)an auto untwist module connected to respond to said error data and tocontrol the turbine yaw motor.
 6. The system of claim 5 wherein the autountwist module is also connected to be responsive to twist state of aturbine platform to control the turbine yaw motor.
 7. The system ofclaim 1 wherein the modules include a fault module for controlling aturbine brake, and at lest three of the following modules:i) a windtrigger module responsive to input from an anemometer at a towermounting the turbine for signaling the fault module; ii) a yaw moduleresponsive to a prevailing wind direction signal to control a turbineyaw motor for rotating a turbine platform to maintain turbine propelleralignment with wind direction; iii) an auto untwist module responsive totwisting of a turbine mounting platform to signal the fault module; iv)a generator control circuit responsive to turbine speed to signal anoverspeed condition to the fault module; v) a generator temperaturemodule responsive to generator temperature to signal said fault module;vi) a propeller control unit responsive to turbine speed to signal saidfault module; vii) a line voltage and frequency module responsive tomonitored line voltage and frequency to signal said fault module; andviii) a loss of phase module responsive to monitored phase of athree-phase mains system to signal the fault monitor in the event ofphase loss.
 8. The system of claim 7 wherein said modules are separateand discrete, and have individually replaceable circuit boards.